function displayinfo(){
    var info = $("#error").html();
    if(info==""){
        document.getElementById("info").style.display="none";
    }else{
        document.getElementById("info").style.display="block";
    }
}
function hintCheck(info,flag){
    if(info.value==""){
        switch(flag){
            case 1:
                info.placeholder="您的用户名";
                break;
            case 2:
                info.placeholder="您的密码";
                break;
            case 3:
                info.placeholder="确认您的密码";
                break;
            case 4:
                info.placeholder="请输入验证码";
                break;
        }
    }
}